Polycarbonate-polyorganosiloxane copolymer and method for continuously producing same

ABSTRACT

Provided are a polycarbonate-polyorganosiloxane copolymer having a carbon tetrachloride concentration of less than 4 ppm by mass, and the following production method for producing the polycarbonate-polyorganosiloxane copolymer. More specifically, provided is a method of continuously producing a polycarbonate-polyorganosiloxane copolymer, the method comprising the steps of: (A) continuously or intermittently taking a polymerization reaction liquid, which is obtained by polymerizing a dihydric phenol compound, a carbonate precursor, and a specific polyorganosiloxane in the presence of an alkaline compound aqueous solution and a water-insoluble organic solvent, out of a reactor; (B) separating the polymerization reaction liquid taken out in the step (A) into an aqueous phase and a water-insoluble organic solvent phase; (C) washing the water-insoluble organic solvent phase separated in the step (B), followed by separation thereof into an aqueous phase and a water-insoluble organic solvent phase; (D) concentrating the water-insoluble organic solvent phase separated in the step (C); and (E) recovering part or all of the water-insoluble organic solvent removed by evaporation in the step (D), followed by distillation purification thereof in a distillation column, the water-insoluble organic solvent obtained in the step (E) being reused as at least part of the water-insoluble organic solvent in the step (A) or as an extraction solvent for the aqueous phase separated in the step (B), or as both thereof, in the step (E), the distillation purification being performed while a concentration of the polycarbonate-polyorganosiloxane copolymer in a column bottom liquid of the distillation column is controlled to 6% by mass or less.

TECHNICAL FIELD

The present invention relates to a polycarbonate-polyorganosiloxanecopolymer and a method of continuously producing the copolymer, and morespecifically, to a method of continuously producing apolycarbonate-polyorganosiloxane copolymer by interfacial polymerizationmethod.

BACKGROUND ART

A polycarbonate-based resin is a polymer excellent in transparency, heatresistance, and impact resistance and is widely used at present as anengineering plastic in the industrial field.

As a method of producing the polycarbonate-based resin, a methodinvolving allowing an aromatic dihydroxy compound such as bisphenol A,and phosgene to react directly with each other (interfacialpolymerizationmethod) is known as a method of producing a high-qualitypolycarbonate.

As a method of industrially producing a polycarbonate by interfacialpolymerization method, there is adopted a method involving bubblingphosgene into an alkali aqueous solution of a bisphenol to form apolycarbonate oligomer having a reactive chloroformate group, andfurther allowing a condensation reaction (polymerization reaction) ofthe polycarbonate oligomer and the bisphenol to proceed in the presenceof a polymerization catalyst such as a tertiary amine, and an alkaliaqueous solution simultaneously with or successively after the formationof the polycarbonate oligomer. From the viewpoints of solubility,handling properties, and the like, methylene chloride is mainly used asa water-insoluble organic solvent on an industrial scale.

The methylene chloride used in the reaction step is generally recoveredand then reused for the reaction step (see Patent Document 1). Inaddition, waste water after the polymerization reaction, waste waterformed after a washing step, and waste water formed after a granulationstep contain an inorganic material such as sodium chloride and anorganic material such as a phenol and a polycarbonate. In order toremove such organic material from the aqueous phase and clean the wastewater, the organic material is extracted and removed from the wastewater by using an organic solvent, preferably the same water-insolubleorganic solvent as that used in the polycarbonate production step, suchas methylene chloride. The water-insoluble organic solvent containingthe extracted and removed phenol and polymer is reused for thepolymerization reaction step (see Patent Document 2).

In addition, in production of phosgene in the method of producing thepolycarbonate-based resin, carbon tetrachloride (CCl₄) is produced as aby-product and carbon tetrachloride is gradually accumulated in areactor by cyclic use of methylene chloride. Accordingly, aconcentration of carbon tetrachloride in the polycarbonate-based resinto be produced increases. The concentration of carbon tetrachloride inthe polycarbonate-based resin is preferably suppressed to a low levelbecause carbon tetrachloride is responsible for deterioration in colortone of the polycarbonate-based resin and corrosion of a die. As amethod of suppressing the concentration of carbon tetrachloride in thepolycarbonate-based resin to a low level, there has been known a methodinvolving producing phosgene with a catalyst layer diluted with amaterial substantially inert to carbon monoxide and chlorine to reducean amount of carbon tetrachloride to be produced as a by-product at thetime of the production of phosgene (see Patent Document 3), or a methodinvolving purifying circulating methylene chloride by distillation inthe production of the polycarbonate-based resin (see Patent Document 4).

It should be noted that, among the polycarbonate-based resins, apolycarbonate-polyorganosiloxane polymer (hereinafter sometimes referredto as “PC-POS”) has been attracting attention because of its high impactresistance, high chemical resistance, and high flame retardancy, and thepolymer has been expected to find utilization in a wide variety offields such as the field of electrical and electronic equipment and thefield of an automobile. As a method of producing the PC-POS, there isknown a method involving allowing a dihydric phenol-based compound andphosgene to react with each other to produce a polycarbonate oligomer,and polymerizing the polycarbonate oligomer with a polyorganosiloxane inthe presence of methylene chloride, an alkaline compound aqueoussolution, a dihydric phenol-based compound, and a polymerizationcatalyst (see Patent Document 5).

CITATION LIST Patent Document

-   [Patent Document 1] JP 2009-132756 A-   [Patent Document 2] JP 2009-285533 A-   [Patent Document 3] JP 08-157206 A-   [Patent Document 4] JP 63-268736 A-   [Patent Document 5] JP 06-329781 A

SUMMARY OF INVENTION Technical Problem

The method described in Patent Document 3 and the method described inPatent Document 4 are each preferably adopted in the production of thePC-POS as well. However, studies made by the inventors of the presentinvention have found the following. When the distillation of methylenechloride is performed, a reboiler at the bottom portion of adistillation column causes a heat transfer failure owing to the foamingof methylene chloride, and hence stable driving of the distillationcolumn cannot be performed in some cases. In addition, even when a flashdrum is used, the discharge pressure of a circulating pump at the bottomportion of the flash drum may be destabilized. As a result, unlike theproduction of a normal polycarbonate-based resin, the concentration ofcarbon tetrachloride tends to increase and hence it is difficult tocontinuously produce a PC-POS having a carbon tetrachlorideconcentration of less than 4 ppm by mass in an industrially stablemanner.

In view of the foregoing, an object of the present invention is toprovide a polycarbonate-polyorganosiloxane copolymer (PC-POS) having acarbon tetrachloride concentration of less than 4 ppm by mass and amethod of continuously producing the PC-POS in an industrially stablemanner.

Solution to Problem

The inventors of the present invention have made extensive studies, andas a result, have found that when the concentration of a PC-POS includedin a column bottom liquid at the bottom portion of a distillation columnexceeds a predetermined value upon distillation of methylene chloridefor reuse, the foaming of methylene chloride occurs to cause theproblem.

In view of the foregoing, the inventors have found that when theconcentration of the PC-POS included in the column bottom liquid iscontrolled to a value equal to or less than the predetermined value by,for example, taking the column bottom liquid out of the bottom portionof the column at the time of the distillation, the foaming of methylenechloride is suppressed and its distillation purification can beefficiently performed, and by extension, a PC-POS having a carbontetrachloride concentration of less than 4 ppm by mass can becontinuously produced in an industrially stable manner.

That is, the present invention relates to the following items [1] to[9].

[1] A polycarbonate-polyorganosiloxane copolymer, having a carbontetrachloride concentration of less than 4 ppm by mass.

[2] The polycarbonate-polyorganosiloxane copolymer according to the item[1], in which the copolymer has a viscosity-average molecular weight of10,000 to 30,000.

[3] A method of continuously producing thepolycarbonate-polyorganosiloxane copolymer according to the item [1] or[2],

the method comprising the steps of:

(A) continuously or intermittently taking a polymerization reactionliquid, which is obtained by polymerizing a dihydric phenol compoundrepresented by the following general formula (1), a carbonate precursor,and a polyorganosiloxane represented by the following general formula(2) in the presence of an alkaline compound aqueous solution and awater-insoluble organic solvent, out of a reactor;

(B) separating the polymerization reaction liquid taken out in the step(A) into an aqueous phase and a water-insoluble organic solvent phase;

(C) washing the water-insoluble organic solvent phase separated in thestep (B), followed by separation thereof into an aqueous phase and awater-insoluble organic solvent phase;

(D) concentrating the water-insoluble organic solvent phase separated inthe step (C); and

(E) recovering part or all of the water-insoluble organic solventremoved by evaporation in the step (D), followed by distillationpurification thereof in a distillation column,

the water-insoluble organic solvent obtained in the step (E) beingreused as at least part of the water-insoluble organic solvent in thestep (A) or as an extraction solvent for the aqueous phase separated inthe step (B), or as both thereof,

in the step (E), the distillation purification being performed while aconcentration of the polycarbonate-polyorganosiloxane copolymer in acolumn bottom liquid of the distillation column is controlled to 6% bymass or less.

In the formula, R¹ and R² each independently represent a halogen atom,an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1to 6 carbon atoms, X represents a single bond, an alkylene group having1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, acycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene grouphaving 5 to 15 carbon atoms, —S—, —SO—, —SO₂—, —O—, or —CO—, and a and beach independently represent an integer of 0 to 4.

In the formula, R³ to R⁶ each independently represent a hydrogen atom, ahalogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy grouphaving 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbonatoms, Y represents a single bond, or an organic residue including analiphatic or aromatic moiety, n represents an average repetition number,Z represents a halogen atom, —R⁷OH, —R⁷—Z′—R⁸—OH, —R⁷COOH, —R⁷NH₂,—COOH, or —SH, the R⁷ represents a substituted or unsubstituted alkylenegroup, a substituted or unsubstituted cycloalkylene group, or asubstituted or unsubstituted arylene group, the R⁸ represents an arylenegroup having 6 to 12 ring-forming carbon atoms, the Z′ represents analkylene group having 1 to 8 carbon atoms, an alkylidene group having 2to 8 carbon atoms, a cycloalkylene group having 5 to 10 carbon atoms, ora cycloalkylidene group having 5 to 10 carbon atoms, and m represents 0or 1.

[4] The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to the item [3], inwhich in the step (E), the concentration of thepolycarbonate-polyorganosiloxane copolymer in the column bottom liquidis controlled to fall within the range by taking at least part of thecolumn bottom liquid out of a column bottom portion of the distillationcolumn.

[5] The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to the item [3] or[4], in which in the step (E), the concentration of thepolycarbonate-polyorganosiloxane copolymer in the column bottom liquidof the distillation column is controlled to 5% by mass or less.

[6] The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to any one of theitems [3] to [5], in which a concentration of carbon tetrachloride inthe water-insoluble organic solvent to be reused as at least part of thewater-insoluble organic solvent in the step (A) or as the extractionsolvent for the aqueous phase separated in the step (B), or as boththereof is controlled to less than 20 ppm by mass.

[7] The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to any one of theitems [3] to [6], in which in the step (E), a column top temperature ofthe distillation column is set to 35 to 70° C. and a column bottomtemperature thereof is set to 45 to 80° C.

[8] The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to any one of theitems [3] to [7], in which in the step (E), before part or all of thewater-insoluble organic solvent is recovered and purified bydistillation in the distillation column, the water-insoluble organicsolvent is passed through a flash drum and the concentration of thepolycarbonate-polyorganosiloxane copolymer in the solvent in the flashdrum is controlled to 6% by mass or less.

[9] The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to any one of theitems [3] to [8], in which the step (A) includes the following step(a-1) and the following step (a-2):

step (a-1): allowing the dihydric phenol compound represented by thegeneral formula (1) and the carbonate precursor to react with each otherin the presence of the alkaline compound aqueous solution and thewater-insoluble organic solvent to produce a polycarbonate oligomerhaving a repeating unit represented by the following general formula(I); and

step (a-2): continuously or intermittently taking the polymerizationreaction liquid, which is obtained by polymerizing the dihydric phenolcompound, the polycarbonate oligomer obtained in the step (a-1), and thepolyorganosiloxane represented by the general formula (2) in thepresence of the alkaline compound aqueous solution and thewater-insoluble organic solvent, out of the reactor:

(In the formula, R¹, R², X, a and b are each defined in the same manneras in the foregoing.)

Advantageous Effects of Invention

According to one embodiment of the present invention, even in theproduction of a polycarbonate-polyorganosiloxane copolymer, the foamingof methylene chloride in a distillation column is suppressed and itsdistillation purification can be efficiently performed, and byextension, a polycarbonate-polyorganosiloxane copolymer having a carbontetrachloride concentration of less than 4 ppm by mass can becontinuously produced in an industrially stable manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of an apparatus for producing apolycarbonate-polyorganosiloxane copolymer used in Examples.

DESCRIPTION OF EMBODIMENTS

In the description, a preferred definition can be arbitrarily adopted,and a combination of preferred definitions can be said to be morepreferred.

According to one embodiment of the present invention, there is provideda polycarbonate-polyorganosiloxane copolymer having a carbontetrachloride concentration of less than 4 ppm by mass, and suchpolycarbonate-polyorganosiloxane copolymer can be produced by thefollowing production method.

In this case, the carbon tetrachloride concentration in thepolycarbonate-polyorganosiloxane copolymer of the present invention ispreferably 3 ppm by mass or less, more preferably 2 ppm by mass or less,still more preferably 1 ppm by mass or less. Thepolycarbonate-polyorganosiloxane copolymer of the present invention maycontain carbon tetrachloride as long as its concentration falls withinthe range.

That is, there is provided a method of continuously producing thepolycarbonate-polyorganosiloxane copolymer having a carbon tetrachlorideconcentration of less than 4 ppm by mass,

the method comprising the steps of:

(A) continuously or intermittently taking a polymerization reactionliquid, which is obtained by polymerizing a dihydric phenol compoundrepresented by the following general formula (1), a carbonate precursor,and a polyorganosiloxane represented by the following general formula(2) in the presence of an alkaline compound aqueous solution and awater-insoluble organic solvent, out of a reactor;

(B) separating the polymerization reaction liquid taken out in the step(A) into an aqueous phase and a water-insoluble organic solvent phase;

(C) washing the water-insoluble organic solvent phase separated in thestep (B), followed by separation thereof into an aqueous phase and awater-insoluble organic solvent phase;

(D) concentrating the water-insoluble organic solvent phase separated inthe step (C); and

(E) recovering part or all of the water-insoluble organic solventremoved by evaporation in the step (D), followed by distillationpurification thereof in a distillation column,

the water-insoluble organic solvent obtained in the step (E) beingreused as at least part of the water-insoluble organic solvent in thestep (A) or as an extraction solvent for the aqueous phase separated inthe step (B), or as both thereof,

in the step (E), the distillation purification being performed while aconcentration of the polycarbonate-polyorganosiloxane copolymer in acolumn bottom liquid of the distillation column is controlled to 6% bymass or less.

[In the formula, R¹ and R² each independently represent a halogen atom,an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1to 6 carbon atoms, X represents a single bond, an alkylene group having1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, acycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene grouphaving 5 to 15 carbon atoms, —S—, —SO—, —SO₂—, —O—, or —CO—, and a and beach independently represent an integer of 0 to 4.]

[In the formula, R³ to R⁶ each independently represent a hydrogen atom,a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxygroup having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbonatoms, Y represents a single bond, or an organic residue including analiphatic or aromatic moiety, n represents an average repetition number,Z represents a halogen atom, —R⁷OH, —R⁷—Z′—R⁸—OH, —R⁷COOH, —R⁷NH₂,—COOH, or —SH, the R⁷ represents a substituted or unsubstituted alkylenegroup, a substituted or unsubstituted cycloalkylene group, or asubstituted or unsubstituted arylene group, the R⁸ represents an arylenegroup having 6 to 12 ring-forming carbon atoms, the Z′ represents analkylene group having 1 to 8 carbon atoms, an alkylidene group having 2to 8 carbon atoms, a cycloalkylene group having 5 to 10 carbon atoms, ora cycloalkylidene group having 5 to 10 carbon atoms, and m represents 0or 1.]

Examples of the halogen atom that R¹ and R² in the general formula (1)each independently represent include a fluorine atom, a chlorine atom, abromine atom, and an iodine atom.

Examples of the alkyl group that R¹ and R² each independently representinclude a methyl group, an ethyl group, a n-propyl group, an isopropylgroup, various butyl groups (“various” means that a linear group and anybranched group are included, and the same holds true for the following),various pentyl groups, and various hexyl groups. An example of thealkoxy group that R¹ and R² each independently represent is an alkoxygroup whose alkyl group moiety is the alkyl group described above.

The alkylene group represented by X is, for example, a methylene group,an ethylene group, a trimethylene group, a tetramethylene group, or ahexamethylene group, and is preferably an alkylene group having 1 to 5carbon atoms. Examples of the alkylidene group represented by X includean ethylidene group and an isopropylidene group. The cycloalkylene grouprepresented by X is, for example, a cyclopentanediyl group, acyclohexanediyl group, or a cyclooctanediyl group, and is preferably acycloalkylene group having 5 to 10 carbon atoms. The cycloalkylidenegroup represented by X is, for example, a cyclohexylidene group, a3,5,5-trimethylcyclohexylidene group, or a 2-adamantylidene group, andis preferably a cycloalkylidene group having 5 to 10 carbon atoms, morepreferably a cycloalkylidene group having 5 to 8 carbon atoms.

a and b each independently represent an integer of 0 to 4, preferably 0to 2, more preferably 0 or 1.

Examples of the halogen atom that R³ to R⁶ in the general formula (2)each independently represent include a fluorine atom, a chlorine atom, abromine atom, and an iodine atom. Examples of the alkyl group or alkoxygroup that R³ to R⁶ each independently represent include the sameexamples as those in the cases of R¹ and R². Examples of the aryl groupthat R³ to R⁶ each independently represent include a phenyl group and anaphthyl group.

The organic residue containing an aliphatic moiety represented by Y is,for example, an alkylene group having 1 to 10 carbon atoms (preferably 1to 6 carbon atoms, more preferably 1 to 3 carbon atoms). In addition,examples of the organic residue containing an aromatic moietyrepresented by Y include arylene groups each having 6 to 12 ring-formingcarbon atoms such as a phenylene group, a naphthylene group, and abiphenyldiyl group.

Examples of the halogen atom represented by Z in the general formula (2)include a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom. Among them, a chlorine atom is preferred.

Examples of the alkylene group represented by R⁷ in −R⁷OH, —R⁷—Z′—R⁸—OH,—R⁷COOH, and —R⁷NH₂ each represented by Z include alkylene groups eachhaving 1 to 10 (preferably 1 to 5) carbon atoms such as a methylenegroup, an ethylene group, a propylene group, a trimethylene group, and apentamethylene group. In addition, examples of the cycloalkylene grouprepresented by the R⁷ include cycloalkylene groups each having 3 to 10(preferably 4 to 8) ring-forming carbon atoms such as a cyclopentylenegroup and a cyclohexylene group. Examples of the arylene grouprepresented by the R⁷ include arylene groups each having 6 to 12ring-forming carbon atoms such as a phenylene group, a naphthylenegroup, and a biphenyldiyl group.

The R⁷ may be substituted with an alkyl group having 1 to 5 carbonatoms, an alkoxy group having 1 to 5 carbon atoms, an aryl group having6 to 12 ring-forming carbon atoms, or the like. Examples of the alkylgroup include a methyl group, an ethyl group, a propyl group, andvarious butyl groups. An example of the alkoxy group is an alkoxy groupwhose alkyl group moiety is the alkyl group described above. An exampleof the aryl group is a phenyl group.

Examples of the arylene group represented by R⁸ include a phenylenegroup, a methoxy-substituted phenylene group, a naphthylene group, and abiphenylylene group.

Examples of the alkylene group, alkylidene group, cycloalkylene group,or cycloalkylidene group represented by Z′ include the same examples asthose in the case of X. Z′ represents preferably an alkylidene grouphaving 2 to 8 carbon atoms, more preferably an isopropylidene group.

In addition, the average repetition number n is preferably 25 to 120,more preferably 30 to 100. Further, the n is preferably 30 to 60 in thecase of a short-chain polyorganosiloxane or is preferably 70 to 100 inthe case of a long-chain polyorganosiloxane.

Examples of the dihydric phenol compound represented by the generalformula (1) include: bis(hydroxyaryl)alkanes such as2,2-bis(4-hydroxyphenyl)propane [trivial name: bisphenol A],bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane,bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl) diphenylmethane,2,2-bis(4-hydroxy-3-methylphenyl)propane,bis(4-hydroxyphenyl)naphthylmethane,1,1-bis(4-hydroxy-t-butylphenyl)propane,2,2-bis(4-hydroxy-3-bromophenyl)propane,2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3-chlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, and2,2-bis(4-hydroxy-3,5-dibromophenyl)propane;bis(hydroxyaryl)cycloalkanes such as1,1-bis(4-hydroxyphenyl)cyclopentane,1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)-3,5,5-trimethylcyclohexane,2,2-bis(4-hydroxyphenyl)norbornane, and1,1-bis(4-hydroxyphenyl)cyclododecane; dihydroxyaryl ethers such as4,4′-dihydroxydiphenyl ether and 4,4′-dihydroxy-3,3′-dimethylphenylether; dihydroxydiaryl sulfides such as 4,4′-dihydroxydiphenyl sulfideand 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfide; dihydroxydiarylsulfoxides such as 4,4′-dihydroxydiphenyl sulfoxide and4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfoxide; dihydroxydiaryl sulfonessuch as 4,4′-dihydroxydiphenyl sulfone and4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfone; dihydroxydiphenyls such as4,4′-dihydroxydiphenyl; dihydroxydiarylfluorenes such as9,9-bis(4-hydroxyphenyl)fluorene and9,9-bis(4-hydroxy-3-methylphenyl)fluorene; dihydroxydiaryladamantanessuch as 1,3-bis(4-hydroxyphenyl)adamantane,2,2-bis(4-hydroxyphenyl)adamantane, and1,3-bis(4-hydroxyphenyl)-5,7-dimethyladamantane;4,4′-[1,3-phenylenebis(1-methylethylidene)]bisphenol;10,10-bis(4-hydroxyphenyl)-9-anthrone; and1,5-bis(4-hydroxyphenylthio)-2,3-dioxapentaene. Among them,2,2-bis(4-hydroxyphenyl)propane [trivial name: bisphenol A] ispreferred.

One of those dihydric phenol compounds may be used alone, or two or morethereof may be used as a mixture.

Examples of the carbonate precursor include carbonyl halides, carbonicacid diesters and haloformates, and specific examples thereof includephosgene, diphenyl carbonate and a dihaloformate of a dihydric phenolcompound. Among them, phosgene is preferred.

In addition, the polyorganosiloxane represented by the general formula(2) can be easily produced by subjecting a phenol having an olefinicallyunsaturated carbon-carbon bond (preferably, for example, vinylphenol,allylphenol, eugenol, or isopropenylphenol) to a hydrosilylationreaction with a terminal of a polyorganosiloxane chain having apredetermined polymerization degree n. The phenol is more preferablyallylphenol or eugenol. In this case, Y in the general formula (2)represents an organic residue derived from allylphenol or eugenol.

Examples of the polyorganosiloxane represented by the general formula(2) include the following.

In the general formulae (3) to (11), R³ to R⁶ are the same as R³ to R⁶in the general formula (2). n is the same as n in the general formula(2). In addition, c represents a positive integer and is preferably aninteger of 1 to 6, more preferably an integer of 1 to 3, still morepreferably 3.

Among them, the phenol-modified polyorganosiloxane represented by thegeneral formula (3) is preferred from the viewpoint of easiness ofpolymerization. Further,α,ω-bis[3-(o-hydroxyphenyl)propyl]polydimethylsiloxane, which is one ofthe compound represented by the general formula (4), orα,ω-bis[3-(4-hydroxy-3-methoxyphenyl)propyl]polydimethylsiloxane, whichis one of the compound represented by the general formula (5), ispreferred from the viewpoint of easiness of availability.

Further, the PC-POS copolymer can be produced by copolymerizing thedihydric phenol represented by the general formula (1), apolyorganosiloxane represented by the following general formula (12),and phosgene, a carbonate, or a chloroformate. In this case, thepolyorganosiloxane represented by the following general formula (12) isa reaction product of the polyorganosiloxane represented by the generalformula (2) and a diisocyanate compound.

In the general formula (12), R³ to R⁶, n, m, Y, and Z are each definedin the same manner as that in the general formula (2), and preferredexamples thereof are also the same as those of the symbols in theformula.

Z¹ represents a divalent group derived from Z in the polyorganosiloxanerepresented by the general formula (2) after the reaction of Z with an—NCO group of the diisocyanate compound.

In addition, β represents a divalent group derived from the diisocyanatecompound or from a dicarboxylic acid compound, and examples thereofinclude divalent groups each represented by any one of the followinggeneral formulae (12-1) to (12-5).

The phenol-modified polyorganosiloxane can be produced by a knownmethod. For example, the following is available as the known productionmethod.

Cyclotrisiloxane and disiloxane are allowed to react with each other inthe presence of an acid catalyst to synthesize anα,ω-dihydrogenorganopolysiloxane. At this time, an α,ω-dihydrogenorganopolysiloxane having a desired average repeating unit can besynthesized by changing a loading ratio between cyclotrisiloxane anddisiloxane. Next, the α,ω-dihydrogen organopolysiloxane is subjected toan addition reaction with a phenol compound having an unsaturatedaliphatic hydrocarbon group such as allylphenol or eugenol in thepresence of a catalyst for a hydrosilylation reaction, whereby aphenol-modified polyorganosiloxane having a desired average repeatingunit can be produced.

In addition, at this stage, a cyclic polyorganosiloxane having a lowmolecular weight and an excessive amount of the phenol compound remainas impurities. Accordingly, those low-molecular weight compounds areremoved by evaporation through heating under reduced pressure.

(Polycarbonate-Polyorganosiloxane Copolymer: PC-POS)

A PC-POS obtained by the production method of the present invention hasa repeating unit represented by the following general formula (I) and aconstituent unit represented by the following general formula (II):

[in the formulae, R¹ to R⁶, X, Y, a, b and n are the same as definedabove].

In the PC-POS, the content of the constituent unit represented by thegeneral formula (II) is not particularly limited, but is preferably 1 to25% by mass, more preferably 2 to 10% by mass. When the content is 1% bymass or more, the impact resistance is excellent, and when the contentis 25% by mass or less, the heat resistance is satisfactory.

In addition, in the PC-POS, the average repeating number n in theconstituent unit represented by the general formula (II) is preferably25 to 120, more preferably 30 to 100. Further, the n is preferably 30 to60 in the case of a short-chain polyorganosiloxane or is preferably 70to 100 in the case of a long-chain polyorganosiloxane. In the PC-POS,when n represents 25 or more, the impact resistance is excellent, andwhen n represents 120 or less, the transparency is satisfactory.

The viscosity-average molecular weight (Mv) of the PC-POS is notparticularly limited, but is preferably 10,000 to 30,000, morepreferably 13,000 to 25,000, more preferably 15,000 to 23,000, morepreferably 15,000 to 21,000, more preferably 16,000 to 20,000,particularly preferably 16,000 to 18,000. When the viscosity-averagemolecular weight of the PC-POS falls within the range, the strength of amolded article is sufficient, the viscosity of the copolymer does notbecome excessively large, and the productivity at the time of productionis stable.

It should be noted that the viscosity-average molecular weight (Mv) inthe description is calculated from the following relational expression(Schnell's equation) by measuring the limiting viscosity [q] of amethylene chloride solution at 20° C. with an Ubbelohde-type viscositytube.[η]=1.23×10⁻⁵ ×Mv ^(0.83)[Method of Producing Polycarbonate-Polyorganosiloxane Copolymer]

As described above, the method of producing apolycarbonate-polyorganosiloxane copolymer (PC-POS) according to thepresent invention includes the step (A) to the step (E).

(Step (A))

The step (A) is a step of continuously or intermittently taking apolymerization reaction liquid, which is obtained by polymerizing adihydric phenol compound represented by the general formula (1), acarbonate precursor, and a polyorganosiloxane represented by the generalformula (2) in the presence of an alkaline compound aqueous solution anda water-insoluble organic solvent, out of a reactor. In the step (A),the polymerization can also be performed in the presence of apolymerization catalyst or a molecular weight modifier, as necessary.The alkaline compound aqueous solution, the water-insoluble organicsolvent, the polymerization catalyst, and the molecular weight modifierare described below.

Although there is no particular limitation, from the viewpoint ofincreasing the transparency of the PC-POS, the step (A) preferablyincludes the following step (a-1) and the following step (a-2):

step (a-1): allowing a dihydric phenol compound represented by thegeneral formula (1) and a carbonate precursor to react with each otherin the presence of an alkaline compound aqueous solution and awater-insoluble organic solvent to produce a polycarbonate oligomerhaving a repeating unit represented by the general formula (I); and

step (a-2): continuously or intermittently taking a polymerizationreaction liquid, which is obtained by polymerizing the dihydric phenolcompound, the polycarbonate oligomer obtained in the step (a-1), and apolyorganosiloxane represented by the general formula (2) in thepresence of an alkaline compound aqueous solution and a water-insolubleorganic solvent, out of a reactor.

(Step (a-1))

In the step (a-1), the reaction between the dihydric phenol compound andthe carbonate precursor is not particularly limited, a known method canbe adopted, and it is preferred to carry out the reaction in thepresence of an alkaline compound aqueous solution and a water-insolubleorganic solvent by the interfacial polymerization method. As necessary,the reaction can also be carried out in the presence of a polymerizationcatalyst, and it is preferred that the reaction be carried out in such amanner.

Examples of the alkaline compound include alkali metal hydroxides suchas sodium hydroxide and potassium hydroxide; and alkaline earth metalhydroxides such as magnesium hydroxide and calcium hydroxide. Amongthem, an alkali metal hydroxide is preferred, and sodium hydroxide ismore preferred. It should be noted that the dihydric phenol compound ispreferably used as a mixture with the alkaline compound aqueoussolution.

As the water-insoluble organic solvent, for example, a halogenatedhydrocarbon such as methylene chloride, chlorobenzene or chloroform ispreferred, and methylene chloride is more preferred.

Examples of the polymerization catalyst include tertiary amines andquaternary ammoniumsalts. Examples of the tertiary amine includetrimethylamine, triethylamine, and tripropylamine. Examples of thequaternary ammonium salt include trimethylbenzylammonium chloride andtriethylammonium chloride. As the polymerization catalyst, a tertiaryamine is preferred, and triethylamine is more preferred.

In the step (a-1), a molecular weight modifier may be used, asnecessary. The molecular weight modifier is not particularly limited solong as the modifier is a monohydric phenol, and examples thereofinclude phenol, o-n-butylphenol, m-n-butylphenol, p-n-butylphenol,o-isobutylphenol, m-isobutylphenol, p-isobutylphenol, o-t-butylphenol,m-t-butylphenol, p-t-butylphenol, o-n-pentylphenol, m-n-pentylphenol,p-n-pentylphenol, o-n-hexylphenol, m-n-hexylphenol, p-n-hexylphenol,p-t-octylphenol, o-cyclohexylphenol, m-cyclohexylphenol,p-cyclohexylphenol, o-phenylphenol, m-phenylphenol, p-phenylphenol,o-nonylphenol, m-nonylphenol, p-nonylphenol, o-cumylphenol,m-cumylphenol, p-cumylphenol, o-naphthylphenol, m-naphthylphenol,p-naphthylphenol, 2,5-di-t-butylphenol, 2,4-di-t-butylphenol,3,5-di-t-butylphenol, 2,5-dicumylphenol, 3,5-dicumylphenol, p-cresol,p-bromophenol, 2,4,6-tribromophenol, a monoalkylphenol having a linearor branched alkyl group having 12 to 35 carbon atoms on average at theortho-, meta-, or para-position,9-(4-hydroxyphenyl)-9-(4-methoxyphenyl)fluorene,9-(4-hydroxy-3-methylphenyl)-9-(4-methoxy-3-methylphenyl)fluorene, and4-(1-adamantyl)phenol. Among them, p-t-butylphenol, p-cumylphenol, andp-phenylphenol are preferred, and p-t-butylphenol is more preferred.

It should be noted that the molecular weight modifier is preferably usedafter dissolution in a water-insoluble organic solvent so that itsconcentration may become preferably 2 to 20% by mass, more preferably 4to 15% by mass, still more preferably 4 to 12% by mass. Examples of thewater-insoluble organic solvent include the same solvents as thosedescribed above. Among them, methylene chloride is preferred.

Although an embodiment of the reaction is not particularly limited,preferred is a method involving continuously or intermittently supplyingthe alkaline compound aqueous solution of a dihydric phenol compound,the water-insoluble organic solvent, and the carbonate precursor into areactor, and as necessary, adding the polymerization catalyst aqueoussolution thereto, while keeping the temperature of the reaction liquidat 40° C. or less, to thereby perform the reaction.

The weight-average molecular weight (Mw) of the thus obtainedpolycarbonate oligomer is preferably 500 to 3,000, more preferably 700to 2,000, still more preferably 800 to 1,500.

The reaction mixed liquid obtained in the step (a-1) is separated intoan aqueous phase and a water-insoluble organic solvent phase, and thewater-insoluble organic solvent phase containing the polycarbonateoligomer is used in the step (a-2). Meanwhile, there may be the casewhere the polycarbonate oligomer or the dihydric phenol compound is alsoincorporated into the aqueous phase. Then, with respect to the aqueousphase, it is preferred that such an organic material be extracted with awater-insoluble organic solvent, and the resultant extract be used as apart or the whole of the water-insoluble organic solvent to be used inthe step (a-2). It is preferred to perform the extraction operation bymixing the aqueous phase with an aqueous phase that is obtained bywashing with an acidic aqueous solution in a step (C) to be describedbelow and then separating.

(Step (a-2))

The step (a-2) is a step of continuously or intermittently taking apolymerization reaction liquid, which is obtained by polymerizing thedihydric phenol compound, the polycarbonate oligomer obtained in thestep (a-1), and a polyorganosiloxane represented by the general formula(2) in the presence of an alkaline compound aqueous solution and awater-insoluble organic solvent, out of a reactor. As necessary, thereaction can also be carried out in the presence of a polymerizationcatalyst, and it is preferred that the reaction be carried out in such amanner.

An embodiment of the polymerization reaction in the step (a-2) is notparticularly limited, and a known method can be adopted. However, fromthe viewpoint of reducing the amount of the unreacted PDMS as much aspossible, it is preferred to divide the polymerization reaction into apreliminary polymerization step and a main polymerization step.

(Preliminary Polymerization Step)

The preliminary polymerization step is a step of continuously orintermittently supplying a polycarbonate oligomer having the repeatingunit represented by the general formula (I) and a water-insolubleorganic solvent, a polyorganosiloxane represented by the general formula(2), a water-insoluble organic solvent, and an alkaline compound aqueoussolution, to thereby perform the reaction. As necessary, the reactioncan also be carried out in the presence of a polymerization catalyst,and it is preferred that the reaction be carried out in such a manner.

In this step, operation procedures are preferred in which thepolycarbonate oligomer having the repeating unit represented by thegeneral formula (I) and the water-insoluble organic solvent, and thepolyorganosiloxane represented by the general formula (2) are suppliedand mixed; thereafter, the polymerization catalyst is supplied, asnecessary; and subsequently, the alkaline compound aqueous solution issupplied and mixed.

(Main Polymerization Step)

The main polymerization step is a step of, after cooling the preliminarypolymerization liquid obtained in the preliminary polymerization step to25° C. or less, continuously or intermittently supplying an alkalinecompound aqueous solution of the dihydric phenol compound represented bythe general formula (1) and a molecular weight modifier thereto andmixing to perform the main polymerization, and continuously orintermittently taking the resultant polymerization reaction liquid outof a reactor. As necessary, the main polymerization can also be carriedout in the presence of a polymerization catalyst, and it is preferredthat the main polymerization be carried out in such a manner.

In the preliminary polymerization step, it is preferred that each of thepolyorganosiloxane and the polycarbonate oligomer on the occasion ofmixing the polyorganosiloxane be dissolved in or mixed with thewater-insoluble organic solvent. In that case, the concentration of thepolyorganosiloxane is preferably 10 to 30% by mass, more preferably 15to 25% by mass. The solid content concentration of the polycarbonateoligomer solution is set to preferably 300 g/L or less, more preferably170 to 250 g/L, still more preferably 180 to 240 g/L. With this, thetransparency of the polycarbonate-polyorganosiloxane copolymer can beincreased. This is because the compatibility between thepolyorganosiloxane and the polycarbonate oligomer is low, and hence,when the polyorganosiloxane concentration or the polycarbonate oligomerconcentration (solid content concentration) is too high, thepolyorganosiloxane tends to exist in a dispersed state in thepolycarbonate oligomer. When the polyorganosiloxane concentration is setto 10 to 30% by mass, and the polycarbonate oligomer concentration isset to 300 g/L or less, the polyorganosiloxane can be quickly andsufficiently dissolved in the polycarbonate oligomer solution with ease,and hence the uniformity of the polymerization reaction is enhanced. Asa result, a polycarbonate-polyorganosiloxane copolymer having excellenttransparency tends to be obtained.

A supply ratio between the supply rate of the polycarbonate oligomer andthe supply rate of the polyorganosiloxane [polycarbonateoligomer:polyorganosiloxane] may be appropriately set in considerationof the composition of the PC-POS to be produced.

In the preliminary polymerization step, the polymerization catalyst ispreferably used as a solution of a water-insoluble organic solvent fromthe viewpoint of enhancing the uniformity of the reaction to increasethe transparency of the polycarbonate-polyorganosiloxane copolymer to beobtained. Examples of the water-insoluble organic solvent include thesame solvents as those described above. Among them, methylene chlorideis preferred from the viewpoint of enhancing the dispersibility of thepolymerization catalyst. The concentration of the polymerizationcatalyst in the polymerization catalyst solution is preferably 0.05 to5% by mass, more preferably 0.1 to 5% by mass.

In the preliminary polymerization step, the alkaline compound ispreferably used as an alkaline compound aqueous solution. In addition,in that case, it is preferred to set the concentration of the alkalinecompound aqueous solution (hereinafter abbreviated as alkaliconcentration) to 2 to 15% by mass. On the occasion of the preliminarypolymerization, the alkaline compound is consumed by three reactionsincluding (1) a reaction between the polycarbonate oligomer and thepolyorganosiloxane, (2) a reaction between a chloroformate group of thepolycarbonate oligomer and a hydroxyl group, and (3) a decompositionreaction of a chloroformate group of the polycarbonate oligomer. Whenthe alkali concentration of the alkaline compound aqueous solution to besupplied is 15% by mass or less, the progress of the reaction (3) can besuppressed from the standpoint of a reaction rate, and an increase inthe amount of the unreacted polyorganosiloxane can be suppressed. Thealkali concentration of the alkaline compound aqueous solution to besupplied at the time of preliminary polymerization is preferably 3 to15% by mass, more preferably 3 to 12% by mass from the viewpoints ofreaction efficiency of the polyorganosiloxane and transparency of thepolycarbonate-polyorganosiloxane copolymer.

It should be noted that the preliminary polymerization is carried out byan interfacial polymerization reaction. In general, in the case of aninterfacial polymerization reaction, there are included two ways of thecase where the aqueous phase is a continuous phase and the case wherethe water-insoluble organic solvent phase is a continuous phase, and inorder to obtain a PC-POS having excellent transparency, it is preferredthat the water-insoluble organic solvent phase be a continuous phase.For the purpose of increasing the uniformity of a reaction between thepolyorganosiloxane and the polycarbonate oligomer in order to obtain thetransparency, the water-insoluble organic solvent phase is stirred as acontinuous phase and then the uniformity between both of thepolyorganosiloxane and the polycarbonate oligomer can be increased,because both of the polyorganosiloxane and the polycarbonate oligomerexist in the water-insoluble organic solvent phase.

In the main polymerization step, the preliminary polymerization liquidobtained in the preliminary polymerization step is preferably oncecooled to 25° C. or less (preferably about 15 to 20° C.). Thereafter,the alkaline compound aqueous solution of the dihydric phenol compoundrepresented by the general formula (1) and the molecular weight modifier(chain-end terminator), and as necessary, a polymerization catalyst arecontinuously or intermittently supplied and mixed to perform the mainpolymerization.

With respect to the alkaline compound, the molecular weight modifier(chain-end terminator), and the polymerization catalyst, the samematerials as those described above are exemplified, and preferredmaterials are also the same. It should be noted that the molecularweight modifier is preferably used after dissolved in a water-insolubleorganic solvent so that its concentration may become preferably 2 to 20%by mass, more preferably 4 to 15% by mass, still more preferably 4 to12% by mass. Examples of the water-insoluble organic solvent include thesame solvents as those described above. Among them, methylene chlorideis preferred.

The thus obtained polymerization reaction liquid is continuously orintermittently taken out of a reactor and transferred into the step (B).

(Step (B))

The step (B) is a step of separating the polymerization reaction liquidtaken out in the step (A) (referring to the polymerization reactionliquid taken out after the step (a-2) in the case where the step (A)includes the step (a-1) and the step (a-2)) into an aqueous phase and awater-insoluble organic solvent phase. The method for the separation isnot particularly limited, and standing separation may be adopted. Fromthe viewpoint of making the separated state between the aqueous phaseand the water-insoluble organic solvent phase satisfactory, it ispreferred to perform centrifugation. Although the centrifugationcondition is not particularly limited, in general, a rotational speed ispreferably about 1,000 to 3,000 rpm.

The aqueous phase obtained in the step (B) is preferably reused in thestep (A), especially the step (a-1) from the viewpoint of a productioncost because the aqueous phase contains the dihydric phenol compound orthe alkaline compound.

(Step (C))

The step (C) is a step of washing the water-insoluble organic solventphase obtained in the step (B), followed by its separation into anaqueous phase and a water-insoluble organic solvent phase. A method forthe washing is, for example, alkali washing, acid washing, or waterwashing, and at least the acid washing and the water washing arepreferably performed.

[Alkali Washing]

In many cases, the water-insoluble organic solvent phase obtained in thestep (B) contains a trace amount of the dihydric phenol compound, andtherefore, it is preferred to wash the water-insoluble organic solventphase with an alkali aqueous solution (hereinafter sometimes referred toas alkali washing).

Examples of the alkaline compound to be used for the alkali aqueoussolution include the same materials as those used in the step (A), andit is preferred to use the same material. Although the temperature atwhich the phase is washed is not particularly limited as long as thetemperature is equal to or less than the boiling point of thewater-insoluble organic solvent, the washing temperature is preferably37° C. or less, more preferably 34° C. or less, still more preferably30° C. or less, particularly preferably 28° C. or less.

After the washing with the alkali aqueous solution, the resultant isseparated into an aqueous phase and a water-insoluble organic solventphase. On this occasion, the method for the separation is notparticularly limited, and standing separation may be adopted. From theviewpoint of making the separated state between the aqueous phase andthe water-insoluble organic solvent phase satisfactory, it is preferredto perform centrifugation at the above-mentioned rotational speed.Although the amount of the alkali aqueous solution to be used for thewashing is not particularly limited, the amount is preferably about 5 to40% by volume, more preferably 5 to 30% by volume, still more preferably10 to 20% by volume in the whole liquid, from the viewpoints of awashing effect and a reduction in the generation amount of waste water.When the amount of the alkali aqueous solution is 40% by volume or less,the continuous phase does not change from the organic phase to theaqueous phase, and the extraction efficiency from the organic phase canbe kept high.

The aqueous phase obtained in the alkali washing step is preferablyreused in the step (A), especially the step (a-1) from the viewpoint ofa production cost because the aqueous phase contains the dihydric phenolcompound or the alkaline compound.

[Acid Washing]

The water-insoluble organic solvent phase separated in the step (B) orthe water-insoluble organic solvent phase after the alkali washing ispreferably washed with an acidic aqueous solution (hereinafter sometimesreferred to as acid washing). The acid washing can remove thepolymerization catalyst or a trace amount of the alkaline compound thatmay be present in the water-insoluble organic solvent phase. An acid tobe used in the preparation of the acidic aqueous solution is, forexample, hydrochloric acid or phosphoric acid. Among them, hydrochloricacid is preferred. However, the acid is not particularly limitedthereto. Although the temperature at which the phase is washed is notparticularly limited as long as the temperature is equal to or less thanthe boiling point of the water-insoluble organic solvent; the washingtemperature is preferably 37° C. or less, more preferably 34° C. orless, still more preferably 30° C. or less, particularly preferably 28°C. or less.

After the acid washing, the washed phase is separated into an aqueousphase and a water-insoluble organic solvent phase. A method for theseparation is not particularly limited and centrifugal separation can beadopted, but it is sufficient to adopt standing separation.

[Water Washing]

The water-insoluble organic solvent phase to be obtained after thewashing is preferably washed with water once or more, more preferablywashed with water one to three times because the phase tends to containthe acid used in the washing or inorganic matter. In this case, thewater-insoluble organic solvent phase can be evaluated for its cleannesson the basis of the electric conductivity of the aqueous phase after thewashing. A target electric conductivity is preferably 1 mS/m or less,more preferably 0.5 mS/m or less. Although the temperature at which thephase is washed is not particularly limited as long as the temperatureis equal to or less than the boilingpoint of the water-insoluble organicsolvent, the washing temperature is preferably 37° C. or less, morepreferably 34° C. or less, still more preferably 30° C. or less,particularly preferably 28° C. or less.

After the washing with water, the washed phase is separated into anaqueous phase and a water-insoluble organic solvent phase. A method forthe separation at that time is also not particularly limited andcentrifugal separation can be adopted, but it is sufficient to adoptstanding separation. It should be noted that the electric conductivityis a value measured with an electric conductivity-measuring device“DS-7” (manufactured by HORIBA, Ltd.).

Incidentally, the aqueous phase separated in the step (B) or the step(C) contains the PC-POS, and in some cases, the polymerization catalystor the like, and hence the following is preferably adopted from theviewpoint of a production cost: the PC-POS, the polymerization catalyst,or the like is extracted with a water-insoluble organic solvent, andpart or all of the extract is appropriately subjected to adevolatilizing step for carbon dioxide removal or distillation purifyingstep before the aqueous phase is reused in the step (A), especially thestep (a-2). A method described in JP 2005-60599 A can be adopted for thedevolatilizing step. Upon reuse of the water-insoluble organic solventused in the extraction, the water-insoluble organic solvent is typicallytransported with a liquid delivery pump, and hence the concentration ofthe PC-POS in the total amount of the water-insoluble organic solvent tobe reused is set to preferably 2% by mass or less (more preferably 1.5%by mass or less, still more preferably 1% by mass or less) from theviewpoint of suppressing, for example, the occurrence of cavitation inthe liquid delivery pump and from the viewpoint of stably performing adevolatilization operation.

Further, in the present invention, the following is preferably adoptedfrom the viewpoint of a production cost: an aqueous phase obtained byseparating the reaction mixed liquid obtained in the step (a-1) into theaqueous phase and a water-insoluble organic solvent phase is mixed withan aqueous phase obtained by separation after acid washing, theresultant aqueous phase is subjected to extraction with awater-insoluble organic solvent, and part or all of the extract isreused as the water-insoluble organic solvent in the step (A) (providedthat the solvent may contain the dihydric phenol compound, thepolycarbonate oligomer, the polymerization catalyst, or the like).

The water-insoluble organic solvent is removed by evaporation throughthe concentration of the water-insoluble organic solvent phase that hasundergone the step (C) [step (D); concentrating step], and the residueis pulverized [pulverizing step] and dried preferably under reducedpressure at about 80 to 160° C. [drying step] or further granulated[granulating step]. Thus, the PC-POS can be obtained.

In the step (D), the concentration is performed so that the solidcontent concentration of the water-insoluble organic solvent may becomepreferably 30 to 40% by mass, more preferably 30 to 35% by mass.

In addition, in the drying step, the drying is performed so that thesolid content concentration of the water-insoluble organic solvent maypreferably become 99.9% by mass or more (the concentration of methylenechloride in the resin may preferably become less than 1,000 ppm).

In the present invention, part or all of the water-insoluble organicsolvent removed by evaporation in the concentrating step is reused as atleast part of the water-insoluble organic solvent in the step (A) or asa solvent (extraction solvent) for extracting organic matter such as thePC-POS from the aqueous phase separated in the step (B) or each of thewashing steps, or as both thereof after having undergone a step (E) tobe described later. Further, part or all of the water-insoluble organicsolvent obtained in the drying step is preferably reused as at leastpart of the water-insoluble organic solvent in the step (A) or as asolvent (extraction solvent) for extracting organic matter such as thePC-POS from the aqueous phase separated in the step (B) or each of thewashing steps, or as both thereof after having undergone the step (E) tobe described later.

(Step (E))

Upon production of phosgene as a raw material for the PC-POS copolymer,carbon tetrachloride (CCl₄) is produced as a by-product, and hencecarbon tetrachloride is gradually accumulated in a reactor by the cyclicuse of methylene chloride. When the reactor is continuously driven as itis, the concentration of carbon tetrachloride in the PC-POS copolymerbecomes 4 ppm by mass or more, which causes the deterioration of thecolor tone of the PC-POS copolymer and the corrosion of a die. In viewof the foregoing, the water-insoluble organic solvent to be reused needsto be purified by distillation as described in the foregoing in orderthat the concentration of carbon tetrachloride in the PC-POS copolymermay be set to less than 4 ppm by mass. The water-insoluble organicsolvent to be reused may be the water-insoluble organic solvent purifiedby distillation alone, or may be a mixture of the water-insolubleorganic solvent purified by distillation and an undistilledwater-insoluble organic solvent (e.g., the water-insoluble organicsolvent obtained in the step (D)). In all cases, the concentration ofcarbon tetrachloride in the water-insoluble organic solvent is set topreferably less than 20 ppm by mass, more preferably 10 ppm by mass orless, still more preferably 5 ppm by mass or less, particularlypreferably 3 ppm by mass or less. When the concentration of carbontetrachloride in the water-insoluble organic solvent to be reused isreduced as described above, the concentration of carbon tetrachloride inthe PC-POS copolymer can be easily reduced to less than 4 ppm by mass.It should be noted that a flash drum may be placed for preventing theclogging of a distillation column tray.

In this context, further studies made by the inventors of the presentinvention have found that unlike the case of the production of a normalpolycarbonate-based resin, in the production of the PC-POS copolymer,the concentration of carbon tetrachloride in the PC-POS copolymer isliable to increase. The foregoing is assumed to result from: the factthat when the distillation purification of methylene chloride isperformed, a reboiler at the bottom portion of a distillation columncauses a heat transfer failure owing to the foaming of methylenechloride containing a slight amount of the PC-POS copolymer, and hencestable driving of the distillation column cannot be performed in somecases; and the fact that even when a flash drum is used, the dischargepressure of a circulating pump at the bottom portion of the flash drummay be destabilized. In the present invention, the problem has beensolved by controlling the concentration of the PC-POS copolymer in thecolumn bottom liquid of the distillation column to 6% by mass or less.The concentration of the PC-POS copolymer in the column bottom liquid ofthe distillation column is preferably controlled to 5% by mass or less.Although the problem is assumed to be due to the fact that a highconcentration of the PC-POS copolymer in the column bottom liquid hasbeen responsible for the foaming of methylene chloride, the phenomenonis a problem that arises only in the production of the PC-POS copolymerbecause the phenomenon does not arise in a normal polycarbonate resin(e.g., a polycarbonate resin obtained from the dihydric phenol compoundrepresented by the general formula (1) and the carbonate precursor,especially a polycarbonate resin free of any organosiloxane structuralunit).

Although a method of setting the concentration of the PC-POS in thecolumn bottom liquid within the range is not particularly limited, apreferred example thereof is a method involving taking out the columnbottom liquid to reduce the concentration of the PC-POS copolymer.Although the rate at which the column bottom liquid is taken out is notparticularly limited as long as the concentration of the PC-POScopolymer can be set to fall within the range, for example, thefollowing method is given: the column bottom liquid is taken out at aflow rate corresponding to 0.3 to 2% by mass of the amount of thewater-insoluble organic solvent to be fed to the distillation column.

Although a method of monitoring the concentration of the PC-POS in thecolumn bottom liquid is not particularly limited, examples thereofinclude: a method involving sampling the column bottom liquid of thedistillation column during its driving, removing the water-insolubleorganic solvent by evaporation to dryness, and measuring the amount ofthe solid content in the residue; and a method involving placing aconcentration meter.

Although conditions for the distillation purification are notparticularly limited except the foregoing matters, the distillation ispreferably performed with a multistage distillation column having 30 to60 stages under the conditions of a reflux ratio of 0.3 to 5 (preferably1 to 4, more preferably 1 to 3), a pressure of from normal pressure to0.2 MPa (gauge pressure), a column top temperature of 35 to 70° C.(preferably 35 to 45° C.), and a column bottom temperature of 45 to 80°C. (preferably 45 to 60° C.).

In the present invention, the following method can also be preferablyadopted: before part or all of the water-insoluble organic solvent isrecovered and purified by distillation in the distillation column, thewater-insoluble organic solvent is passed through a flash drum and theconcentration of the polycarbonate-polyorganosiloxane copolymer in thesolvent in the flash drum is controlled to 6% by mass or less. Theconcentration of the polycarbonate-polyorganosiloxane copolymer in thewater-insoluble organic solvent in the flash drum is more preferably 5%by mass or less.

It should be noted that the concentration of the PC-POS copolymer in thewater-insoluble organic solvent phase to be reused is controlled topreferably 2% by mass or less, more preferably 1.5% by mass or less,still more preferably 1% by mass or less.

The content of carbon tetrachloride in the PC-POS copolymer obtained asdescribed above is less than 4 ppm by mass, preferably 3 ppm by mass orless, more preferably 2 ppm by mass or less, still more preferably 1 ppmby mass or less, and hence the PC-POS copolymer is a high-quality PC-POScopolymer. According to the present invention, such high-quality PC-POScopolymer can be continuously produced for a long time period. It shouldbe noted that the content of carbon tetrachloride in the PC-POScopolymer is measured by a method described in Examples.

In addition, the amount of a polyorganosiloxane residue in the PC-POScopolymer is preferably 0.1 to 40% by mass, more preferably 1 to 10% bymass, still more preferably 3 to 6.5% by mass.

EXAMPLES

Examples of the present invention are further described. It should benoted that the present invention is by no means limited by Examples. Itshould be noted that in each example, a viscosity-average molecularweight (Mv) and the amount of a polydimethylsiloxane (PDMS) residue in aPC-PDMS were measured in accordance with the following methods. Inaddition, the measurement of the concentration of a PC-PDMS in a columnbottom liquid was performed by a method involving removing awater-insoluble organic solvent by evaporation to dryness and measuringthe amount of the solid content in the residue, and the measurement ofthe concentration of carbon tetrachloride in methylene chloride and themeasurement of the concentration of carbon tetrachloride in a PC-PDMSpellet were performed by gas chromatography measurement under thefollowing conditions.

[1. Amount of Polydimethylsiloxane (PDMS) Residue in PC-PDMS]

The amount was determined by focusing attention on protons of methylgroups in a PDMS by NMR measurement.

[2. Method of Measuring Viscosity-Average Molecular Weight (Mv)]

The viscosity-average molecular weight (Mv) was calculated from thefollowing relational expression (Schnell's equation) by measuring thelimiting viscosity [n] of a methylene chloride solution at 20° C. withan Ubbelohde-type viscosity tube.[η]=1.23×10⁻⁵ ×Mv ^(0.83)[3. Gas Chromatography Measurement Condition]Apparatus: Model number “7890A” (manufactured by Agilent Technologies)Analysis conditions: An injection port temperature of 200° C. and adetector temperature of 220° C.Column: A capillary column (“DB-WAX” manufactured by J & W, filmthickness: 1 μm, inner diameter: 0.53 mm, length: 60 m)Column temperature: The temperature is increased 40° C. to 65° C. at 2°C./min and is increased to 120° C. at 5° C./min.Detector: A hydrogen flame ionization detector (FID)

Synthesis Example 1 Production of Polycarbonate Oligomer Solution (Step(A)-Step (a-1))

To a 5.6% by mass sodium hydroxide aqueous solution, sodium dithionitewas added in an amount of 2,000 ppm by mass relative to bisphenol A tobe dissolved later, and bisphenol A was then dissolved therein so thatthe concentration of bisphenol A became 13.5% by mass, to therebyprepare a solution of bisphenol A in aqueous sodium hydroxide (aqueoussolution of BPNa).

The solution of bisphenol A in aqueous sodium hydroxide, methylenechloride, and phosgene were continuously passed through a tubularreactor having an inner diameter of 6 mm and a tube length of 30 m atflow rates of 40 L/hr, 15 L/hr and 4.0 kg/hr, respectively. The tubularreactor had a jacket portion, and cooling water was passed through thejacket to keep the reaction liquid at a temperature of 40° C. or less.

The reaction liquid that had exited the tubular reactor was continuouslyintroduced into a baffled vessel-type reactor having an internal volumeof 40 L and provided with a sweptback blade, and then, 2.8 L/hr of thesolution of bisphenol A in aqueous sodium hydroxide, 0.07 L/hr of a 25%by mass sodium hydroxide aqueous solution, 17 L/hr of water, and 0.64L/hr of a 1% by mass triethylamine aqueous solution were further addedto the reactor to perform a reaction. The reaction liquid overflown fromthe vessel-type reactor was continuously taken out and allowed to standto separate and remove an aqueous phase, and a methylene chloride phasewas then collected.

The concentration of the thus obtained polycarbonate oligomer solution(methylene chloride solution) was 324 g/L, and the concentration of achloroformate group thereof was 0.74 mol/L. In addition, thepolycarbonate oligomer had a weight-average molecular weight (Mw) of1,190.

It should be noted that the weight-average molecular weight (Mw) wasmeasured as a molecular weight (weight-average molecular weight: Mw) interms of standard polystyrene by GPC (column: TOSOH TSK-GEL MULTIPOREHXL-M (two)+Shodex KF801 (one), temperature: 40° C., flow rate: 1.0ml/min, detector: RI) with tetrahydrofuran (THF) as a developingsolvent.

Example 1

A polycarbonate-polydimethylsiloxane copolymer was continuously producedwith a production apparatus illustrated in FIG. 1. A method for theproduction is specifically as described below.

(Step (A)-Step (a-2))

26 Kilograms per hour of the polycarbonate oligomer (PCO) solution[6.PCO/MC] produced in Synthesis Example 1 and 11.8 kg/hr of methylenechloride[7. MC] were mixed inpiping (PCO concentration: 223 g/L). Then,2.7 kg/hr of a 20% by mass solution of an allylphenol terminal-modifiedpolydimethylsiloxane in which the repetition number n ofdimethylsiloxane units was 90 in methylene chloride [8. PDMS/MC] weremixed with the mixture in the piping. After that, the contents weresufficiently mixed with a static mixer [5 a. SMX] and then the mixedliquid was cooled to 19 to 22° C. with a heat exchanger.

The cooled mixed liquid was mixed with 0.52 kg/hr of a 1% by masssolution of triethylamine (TEA) in methylene chloride[9. TEA/MC] in thepiping and then the contents were sufficiently mixed with a static mixer[5 b. SMX]. After that, 1.84 kg/hr of 6.4% by mass aqueous sodiumhydroxide[10 a. aqueous NaOH] were added to the mixture immediately infront of a reactor [1. Rx-1], and a reaction (preliminarypolymerization) between the polycarbonate oligomer and the allylphenolterminal-modified PDMS was performed in the reactor [1. Rx-1] while amethylene chloride phase was used as a continuous phase. It should benoted that the reactor [1. Rx-1] was a mixer provided with a turbineblade (pipeline homomixer [manufactured by Tokushu Kika Kogyo Co.,Ltd.]) and was driven at a number of rotations of 4,400 rpm.

A preliminary polymerization liquid that had exited the reactor [1.Rx-1] was cooled to 17 to 20° C. with a heat exchanger. After that, amixture obtained by adding 2.3 kg/hr of an 8% by mass solution ofp-t-butylphenol (PTBP) in methylene chloride[13. PTBP/MC] to 0.18 kg/hrof a 1% by mass aqueous solution of triethylamine[11. aqueous solutionof TEA] and 11.2 kg/hr of a solution of bisphenol A in aqueous sodiumhydroxide[12. aqueous solution of BPNa], and mixing the contents in thepiping was added to the preliminary polymerization liquid immediately infront of a reactor [2. Rx-2] After that, 5.1 kg/hr of a 15% by massaqueous NaOH [10b. aqueous NaOH] were added to the mixed liquid and apolymerization reaction (main polymerization) was performed in thereactor [2. Rx-2]. It should be noted that the reactor [2. Rx-2] was amixer provided with a turbine blade and was driven at a number ofrotations of 4,400 rpm. The solution of bisphenol A in aqueous sodiumhydroxide used here was the same as the aqueous solution of BPNa used inSynthesis Example 1.

A polymerization reaction liquid that had exited the reactor [2. Rx-2]was sequentially introduced into a reactor [3. Rx-3] and a reactor [4.Rx-4], and the polymerization reaction was completed while itstemperature was controlled to 38° C. or less. The reactor [3. Rx-3] is areactor having an orifice plate and a cooling jacket, and the reactor[4. Rx-4] is a five-stage tower reactor having a cooling jacket.

(Separating Step (Step (B)))

35 Liters of the polymerization reaction liquid collected from thereactor [4. Rx-4] and 10 L of methylene chloride for dilution werecharged into a 50-L vessel-type washing vessel provided with a baffleboard and a paddle-type stirring blade, and were stirred at 240 rpm for10 minutes. After that, the mixture was left to stand for 1 hour to beseparated into an organic phase containing thepolycarbonate-polydimethylsiloxane copolymer (PC-PDMS), and an aqueousphase containing excessive amounts of bisphenol A and sodium hydroxide,followed by the isolation of the organic phase.

(Alkali Washing, Acid Washing, and Water Washing (Step (C)))

The solution of the polycarbonate-polydimethylsiloxane copolymer(PC-PDMS) in methylene chloride thus obtained was sequentially washedwith 0.03 mol/L aqueous sodium hydroxide and 0.2 mol/L hydrochloric acidin amounts of 15% by volume each with respect to the solution. Next, thesolution was repeatedly washed with pure water so that an electricconductivity in an aqueous phase after the washing became 0.1 mS/m orless.

(Concentrating Step (Step (D)), Drying Step, and Granulating Step)

The solution of the PC-PDMS in methylene chloride thus obtained wasconcentrated [concentrating step], and was then pulverized and driedunder reduced pressure at 120° C. [drying step]. The resultant flake wasfed to an extruder and pelletized. At that time, a preset temperaturewas divided into four sections starting from a screw inlet portion, andthe temperatures of the sections were 260° C., 270° C., 275° C., and275° C., respectively, and the temperature of a die head was set to 270°C. [granulating step].

(Recovery and Distillation Purification of Methylene Chloride (Step(E)))

Meanwhile, methylene chloride separated in each of the concentratingstep and the drying step was recovered in a 4.5-m³ storage tank (MCstorage tank). The concentration of the PC-PDMS in methylene chloride inthe MC storage tank was 195 ppm by mass.

Next, methylene chloride recovered in the MC storage tank was introducedinto the twentieth stage of a distillation column having 40 stages at 52L/hr, and was purified by distillation at a column top temperature of40° C., a column bottom temperature of 50° C., and a column top refluxratio of 2.0. Methylene chloride was purified by distillation from thetop of the column at a recovery ratio of 99.5%.

The following continuous driving was performed: the purified methylenechloride was introduced into the tubular reactor to be used in SynthesisExample 1 and as a reaction solvent in the step (A)-step (a-2), and wasreused. During the continuous driving, the following operation wasperformed: the concentration of the PC-PDMS in the column bottom liquidof the distillation column was periodically measured, part of the columnbottom liquid was taken out and methylene chloride after distillationpurification was fed instead so that the concentration fell within therange of from 1 to 3% by mass. The concentration of the PC-PDMS in thecolumn bottom liquid of the distillation column was around 2% by mass onaverage.

The concentration of carbon tetrachloride in methylene chloride in theMC storage tank after 720 hours of the continuous driving and theconcentration of carbon tetrachloride in the resultant PC-PDMS pelletwere measured.

Table 1 shows the results.

Example 2

The same operations were performed except that in Example 1, during thecontinuous driving, the following operation was performed: theconcentration of the PC-PDMS in the column bottom liquid of thedistillation column was periodically measured, part of the column bottomliquid was taken out and methylene chloride after distillationpurification was fed instead so that the concentration fell within therange of from 3 to 5% by mass. The concentration of the PC-PDMS in thecolumn bottom liquid of the distillation column was around 4% by mass onaverage.

Table 1 shows the results.

Example 3

The same operations were performed except that in Example 2, the supplyamount of the 8% by mass solution of p-t-butylphenol (PTBP) in methylenechloride[13. PTBP/MC] to be added immediately in front of the reactor[2. Rx-2] after the cooling of the preliminary polymerization liquidthat had exited the reactor [1. Rx-1] of the step (A)-step (a-2) withthe heat exchanger to from 17 to 20° C. was changed to 1.8 kg/hr. Theconcentration of the PC-PDMS in the column bottom liquid of thedistillation column was around 4% by mass on average.

Table 1 shows the results.

Comparative Example 1 Case where Methylene Chloride is Reused withoutbeing Purified by Distillation

In Example 1, the following continuous driving was performed: recoveredmethylene chloride was introduced into the tubular reactor to be used inSynthesis Example 1 and as a reaction solvent in the step (A)-step (a-2)without being purified by distillation, and was reused. Theconcentration of carbon tetrachloride in methylene chloride in the MCstorage tank after 200 hours of the continuous driving and theconcentration of carbon tetrachloride in the resultant PC-PDMS pelletwere measured.

Table 1 shows the results.

Comparative Example 2 Case where Concentration of PC-PDMS in ColumnBottom Liquid is not Controlled

The same operations were performed except that in Example 1, theconcentration of the PC-PDMS in the column bottom liquid of thedistillation column was not controlled. After 200 hours of thecontinuous driving, temperature control became difficult owing to a heattransfer failure at the bottom portion of the distillation column.Accordingly, the driving of the distillation column was stopped and thefollowing continuous driving was performed: recovered methylene chloridewas introduced into the tubular reactor to be used in Synthesis Example1 and as a reaction solvent in the step (A)-step (a-2) without beingpurified by distillation, and was reused.

The concentration of carbon tetrachloride in methylene chloride in theMC storage tank after a total of 720 hours of the continuous driving andthe concentration of carbon tetrachloride in the resultant PC-PDMSpellet were measured.

Table 1 shows the results.

Reference Example 1 Case of Continuous Production of NormalPolycarbonate-Based Resin

Continuous production of a polycarbonate was similarly performed exceptthat in Example 1, the 20% by mass solution of an allylphenolterminal-modified polydimethylsiloxane in methylene chloride was notused in the “step (A)-step (a-2)”, and during the continuous driving,the concentration of the PC in the column bottom liquid of thedistillation column was not controlled. Even after 720 hours of thecontinuous driving, no trouble occurred in the distillation column.

The concentration of carbon tetrachloride in methylene chloride in theMC storage tank after 720 hours of the continuous driving and theconcentration of carbon tetrachloride in the resultant polycarbonatepellet were measured.

Table 1 shows the results.

TABLE 1 Reference Example Comparative Example Example 1 2 3 1 2 1Presence or absence of Present Present Present Absent Present Presentdistillation purification [step (E)] Concentration of PC-PDMS in 1 to 33 to 5 3 to 5 — 7  16*¹ column bottom liquid (% by mass) Concentrationof CCl₄ in 2 2 2 20 23 2 MC storage tank (ppm by mass) Concentration ofCCl₄ in Less than 1 Less than 1 Less than 1 4 4 Less than 1*² PC-PDMSpellet (ppm by mass) Continuous driving time 720 720 720 200 720 720 Amount of polydimethylsiloxane 6 6 6 6 6 0 residue in PC-PDMSViscosity-average molecular 17,500 17,800 21,300 17,200 17,300 17,500   weight of PC-PDMS (Mv) *¹Concentration of PC in column bottom liquid (%by mass) *²Concentration of CCl₄ in PC pellet (ppm by mass)

When recovered methylene chloride was reused without being purified bydistillation like Comparative Example 1, the concentration of carbontetrachloride in methylene chloride in the methylene chloride storagetank (MC storage tank) increased, and at the same time, theconcentration of carbon tetrachloride in the PC-PDMS pellet became 4 ppmby mass or more.

In addition, when the concentration of the PC-PDMS in the column bottomliquid of the distillation column was not controlled like ComparativeExample 2, after 200 hours of the continuous driving, temperaturecontrol became difficult owing to a heat transfer failure at the bottomportion of the distillation column, and hence the continuous drivingcould not be performed anymore and there was no choice but to stop thedriving of the distillation column. In addition, it was found that theconcentration of carbon tetrachloride in methylene chloride in themethylene chloride storage tank increased and the concentration ofcarbon tetrachloride in the resultant PC-PDMS also increased.

As compared to the foregoing, in each of Examples 1 to 3, theconcentration of carbon tetrachloride in the PC-PDMS pellet can bemaintained at less than 1 ppm by mass irrespective of long-term driving,and hence the examples are each found to be a method by which ahigh-quality PC-PDMS can be produced in an industrially stable manner.

It should be noted that as shown by the results of Reference Example 1,in the case of the production of a normal polycarbonate, an influence bythe concentration of a polymer in the column bottom liquid of adistillation column was absent unlike the case of the production of aPC-PDMS, and hence even when the concentration of the PC in the columnbottom liquid of the distillation column was 16% by mass, a heattransfer failure at the bottom portion of the distillation column didnot occur and its continuous driving was able to be performed.

INDUSTRIAL APPLICABILITY

The polycarbonate-polydimethylsiloxane copolymer obtained by the presentinvention is expected to find utilization in various fields such as thefield of electrical and electronic equipment and the field of anautomobile. In particular, the polycarbonate-polydimethylsiloxanecopolymer can be utilized as, for example, a material for the casing ofa mobile phone, a mobile personal computer, a digital camera, a videocamera, an electric power tool, or the like, or a material for otherarticles for daily use.

REFERENCE SIGNS LIST

-   1 to 4 reactor-   5 a, 5 b mixer-   6 solution of polycarbonate oligomer-   7 methylene chloride-   8 solution of allylphenol terminal-modified polydimethylsiloxane in    methylene chloride-   9 solution of triethylamine in methylene chloride-   10 a, 10 b aqueous sodium hydroxide-   11 aqueous solution of triethylamine-   12 solution of bisphenol A in aqueous sodium hydroxide-   13 solution of p-t-butylphenol in methylene chloride

The invention claimed is:
 1. A method of continuously producing apolycarbonate-polyorganosiloxane copolymer having a carbon tetrachlorideconcentration of less than 4 ppm by mass, the method comprising: (A)continuously or intermittently taking a polymerization reaction liquid,which is obtained by polymerizing a dihydric phenol compound representedby formula (1), a carbonate precursor, and a polyorganosiloxanerepresented by formula (2) in a presence of an alkaline compound aqueoussolution and a water-insoluble organic solvent, out of a reactor; (B)separating the polymerization reaction liquid taken out in (A) into anaqueous phase and a water-insoluble organic solvent phase; (C) washingthe water-insoluble organic solvent phase separated in (B) with analkali aqueous solution, an acidic aqueous solution, or water, andseparating a resulting mixture into an aqueous phase and awater-insoluble organic solvent phase; (D) concentrating thewater-insoluble organic solvent phase separated in (C); and (E)recovering part or all of the water-insoluble organic solvent removed byevaporation in (D), and subsequently performing distillationpurification of the recovered water-insoluble organic solvent in adistillation column; wherein: the water-insoluble organic solventobtained in (E) is reused as at least part of the water-insolubleorganic solvent in (A), as an extraction solvent for the aqueous phaseseparated in (B), or both; and in (E), the distillation purification isperformed while a concentration of the polycarbonate-polyorganosiloxanecopolymer in a column bottom liquid of the distillation column iscontrolled to 6% by mass or less:

wherein R¹ and R² each independently represent a halogen atom, an alkylgroup having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6carbon atoms, X represents a single bond, an alkylene group having 1 to8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, acycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene grouphaving 5 to 15 carbon atoms, —S—, —SO—, —SO₂—, —O—, or —CO—, and a and beach independently represent an integer of 0 to 4;

wherein R³ to R⁶ each independently represent a hydrogen atom, a halogenatom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, Yrepresents a single bond, or an organic residue including an aliphaticor aromatic moiety, n represents an average repetition number, Zrepresents a halogen atom, —R⁷OH, —R⁷—Z′—R⁸—OH, —R⁷COOH, —R⁷NH₂, —COOH,or —SH, R⁷ represents a substituted or unsubstituted alkylene group, asubstituted or unsubstituted cycloalkylene group, or a substituted orunsubstituted arylene group, R⁸ represents an arylene group having 6 to12 ring-forming carbon atoms, Z′ represents an alkylene group having 1to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, acycloalkylene group having 5 to 10 carbon atoms, or a cycloalkylidenegroup having 5 to 10 carbon atoms, and m represents 0 or
 1. 2. Themethod of continuously producing a polycarbonate-polyorganosiloxanecopolymer according to claim 1, wherein in (E), the concentration of thepolycarbonate-polyorganosiloxane copolymer in the column bottom liquidis controlled to fall within the range by taking at least part of thecolumn bottom liquid out of a column bottom portion of the distillationcolumn.
 3. The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to claim 1, whereinin (E), the concentration of the polycarbonate-polyorganosiloxanecopolymer in the column bottom liquid of the distillation column iscontrolled to 5% by mass or less.
 4. The method of continuouslyproducing a polycarbonate-polyorganosiloxane copolymer according toclaim 1, wherein a concentration of carbon tetrachloride in thewater-insoluble organic solvent reused as at least part of thewater-insoluble organic solvent in (A), as the extraction solvent forthe aqueous phase separated in (B), or both is controlled to less than20 ppm by mass.
 5. The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to claim 1, whereinin (E), a column top temperature of the distillation column is set to 35to 70° C. and a column bottom temperature thereof is set to 45 to 80° C.6. The method of continuously producing apolycarbonate-polyorganosiloxane copolymer according to claim 1, whereinin (E), before part or all of the water-insoluble organic solvent isrecovered and purified by distillation in the distillation column, thewater-insoluble organic solvent is passed through a flash drum and theconcentration of the polycarbonate-polyorganosiloxane copolymer in thesolvent in the flash drum is controlled to 6% by mass or less.
 7. Themethod of continuously producing a polycarbonate-polyorganosiloxanecopolymer according to claim 1, wherein (A) includes (a-1) and (a-2):(a-1): allowing the dihydric phenol compound represented by formula (1)and the carbonate precursor to react with each other in the presence ofthe alkaline compound aqueous solution and the water-insoluble organicsolvent to produce a polycarbonate oligomer having a repeating unitrepresented by formula (I); and (a-2): continuously or intermittentlytaking the polymerization reaction liquid, which is obtained bypolymerizing the dihydric phenol compound, the polycarbonate oligomerobtained in (a-1), and the polyorganosiloxane represented by formula (2)in the presence of the alkaline compound aqueous solution and thewater-insoluble organic solvent, out of the reactor:

wherein R¹, R², X, a and b are each defined as above.